The present invention relates generally to control apparatus for tablet press machinery. More particularly, the invention relates to a control apparatus for measuring compression forces associated with tablet formation, monitoring tableting events such as counting the number of tablets which have been formed by the tablet press, and using this information to control the operation of the press. The invention has particular application to, but is not limited to, a double sided rotary tablet press.
It is known to measure compression forces in the force applying member of a rotary tablet press using electrical circuitry such as strain gauges. See, for example, U.S. Pat. No. 3,255,716 to Knoechel. Knoechel also teaches control circuitry responsive to a compression force signal derived from the strain gauges for adjusting the level of powder fill in the die cavities. It is also known to use a compression force signal to divert "bad" tablets, shut down the tablet press, compute average compression forces and maintain a count of the number of tablets produced by the tablet press. See U.S. Pat. Nos. 3,507,388 to Furtwaengler et. al., 3,389,432 to Griesheimer et. al. 4,238,431 to Stuben et al, 4,062,914 to Hinzpeter, 4,100,598 and 4,121,289 to Stiel, and 4,030,868 to Williams. See also, British Pat. No. 1,216,397 to Marshall (published Dec. 23, 1970).
As is known in the tablet press control art, it is desirable to record the peak compression force applied to powder fill in a die cavity and use this information to produce control signals for effecting the operation of the press. A problem with prior art tablet press controllers is that they do not record the peak compression force with repeated reliability and therefore they are inaccurate. Moreover, known controllers are limited in the number and type of control signals which they can generate and provide to the tablet press. Still further, prior art controllers are cumbersome, expensive and difficult to set up and maintain.
It is therefore desirable to provide a tablet press controller which is highly accurate and is extremely versatile in the type and number of control signals which it can provide to the press. It is also desirable to provide a tablet press controller which is relatively inexpensive, reliable and easy to operate.